Multi-stage resin surface etching method, and plating method on resin using same

ABSTRACT

A novel technique that is a resin etching technique without using chromic acid and can be operated at an industrial level is provided by a resin surface etching method characterized in that, in etching a resin surface, one set of the following steps (a) and (b) is performed two or more times without performing a resin swelling step: (a) a step of treating the resin surface with a solution containing an oxidizing agent and adsorbing the oxidizing agent on the resin surface, and (b) a step of activating the oxidizing agent adsorbed on the resin surface in the step (a).

TECHNICAL FIELD

The present invention relates to a multi-stage resin surface etchingmethod, and a plating method on a resin using the same.

BACKGROUND ART

Conventionally, it is known that when a plastic surface is subjected toa metallization treatment by plating, in order to enhance adhesion ofthe plastic surface to a plating film, an etching treatment forroughening the plastic surface with a mixed liquid of chromic acid andsulfuric acid is performed before a plating treatment.

However, in the etching treatment, the operation is performed at a hightemperature of 60° C. or higher using harmful hexavalent chromium, andtherefore, there was a problem that the operation environment isdeteriorated, and further, attention is needed also for a waste watertreatment thereof.

Further, recently, a technique for etching a plastic surface usingpermanganic acid has also been reported (PTL 1), however, permanganicacid may sometimes be promptly decomposed depending on use conditions,and it was sometimes problematic for industrial use.

Thereafter, in order to suppress decomposition of the etching solutionusing permanganic acid described above, a composition for an etchingtreatment containing permanganic acid, a specific inorganic acid, andfurther one component selected from a halogen oxoacid, a halogen oxoacidsalt, a persulfate, and a bismuthate has also been reported (PTL 2),however, the above-mentioned component is used in a large amount, andtherefore, the cost is high, and this was also problematic forindustrial use.

Further, in order to suppress decomposition of the etching solutionusing permanganic acid described above, a technique in which a resin isswollen with an aqueous dispersion or an aqueous solution containing aspecific organic compound, and thereafter the resin is brought intocontact with an aqueous solution containing permanganic acid, andfurther brought into contact with an aqueous solution containing an acidor the like has also been reported (PTL 3), however, a swelling step isessential, adhesion of plating after etching is sometimes low, etc., andthis was also problematic for industrial use.

CITATION LIST Patent Literature

PTL 1: WO 2005/094394

PTL 2: Japanese Patent No. 5177426

PTL 3: JP-A-2007-100174

SUMMARY OF INVENTION Technical Problem

An object of the present invention is to provide a novel technique thatis a resin etching technique without using chromic acid and can beoperated at an industrial level.

Solution to Problem

The present inventors made intensive studies for achieving the aboveobject, and as a result, they unexpectedly found that by dividing anetching step using an oxidizing agent for a resin into two stages andfurther repeatedly performing the step, a resin surface can besufficiently etched even without performing a resin swelling step, andtherefore, by the subsequent plating, high adhesion is obtained, andthus completed the present invention.

That is, the present invention is directed to a resin surface etchingmethod, characterized in that, in etching a resin surface, one set ofthe following steps (a) and (b) is performed two or more times withoutperforming a resin swelling step:

(a) a step of treating the resin surface with a solution containing anoxidizing agent and adsorbing the oxidizing agent on the resin surface;and

(b) a step of activating the oxidizing agent adsorbed on the resinsurface in the step (a).

Further, the present invention is directed to a plating method on aresin, characterized in that, in plating a resin, the plating isperformed after the resin is etched by the above-mentioned resin surfaceetching method without performing a resin swelling step.

Advantageous Effects of Invention

The resin surface etching method of the present invention can suppressdecomposition of an oxidizing agent used for etching. Further, in theresin surface etching method of the present invention, the etching stepis repeatedly performed, however, etching can be more efficientlyperformed in a shorter time than when the etching step is performed inone stage for a long time. In addition, by the resin surface etchingmethod of the present invention, the resin surface can be sufficientlyetched, and therefore, it is not necessary to perform a resin swellingstep that was conventionally required.

Therefore, when a resin is plated after performing the above-mentionedetching method, a plated product that has high adhesion and canparticularly withstand also a severe heat shock test can be obtained.

DESCRIPTION OF EMBODIMENTS

In the resin surface etching method of the present invention(hereinafter referred to as “method of the present invention”), one setof the following steps (a) and (b) is performed two or more times.Incidentally, even if sufficient etching cannot be achieved by a certainnumber of sets, sufficient etching can be achieved by increasing thenumber of sets.

(a) a step of treating the resin surface with a solution containing anoxidizing agent and adsorbing the oxidizing agent on the resin surface

(b) a step of activating the oxidizing agent adsorbed on the resinsurface in the step (a)

Incidentally, the resin may be subjected to a treatment such asdegreasing, surface conditioning, and the like before performing themethod of the present invention. However, a swelling step forfacilitating resin etching is not performed. Water washing or hot waterwashing may be performed before or after the treatment such asdegreasing, surface conditioning, and the like.

The resin that can be treated with the etching solution of the presentinvention is not particularly limited, but examples thereof includeacrylonitrile-butadiene-styrene (ABS),polycarbonate/acrylonitrile-butadiene-styrene (PC/ABS),acrylonitrile-styrene-acrylate (ASA), silicon-based compositerubber-acrylonitrile-styrene (SAS), NORYL, polypropylene, polycarbonate(PC), acrylonitrile-styrene, polyacetate, polystyrene, polyamide,aromatic polyamides, polyethylene, polyether ketone, polyethyleneterephthalate, polybutylene terephthalate, polysulfone, polyether ethersulfone, polyether imide, modified polyphenylene ether, polyphenylenesulfide, polyamide, polyimide, epoxy resins, liquid crystal polymers,and the like, and copolymers of the above-mentioned respective polymers,and the like. Among these resins, particularly ABS and PC/ABS arepreferred. Further, the shape of the resin is also not particularlylimited.

The oxidizing agent used in the step (a) of the method of the presentinvention is not particularly limited, however, examples thereof includepermanganates such as potassium permanganate, sodium permanganate, andthe like, and manganese salts such as manganese sulfate, manganesenitrate, manganese carbonate, manganese chloride, manganese acetate,manganese dioxide, sodium manganate, potassium manganite, and the like.Among these oxidizing agents, particularly permanganates are preferred.Further, among these oxidizing agents, one type or two or more types canbe used.

As the solution containing the oxidizing agent, for example, a solutionobtained by dissolving the oxidizing agent in a solvent such as water isexemplified. The content of the oxidizing agent in this solution is notparticularly limited, but is, for example, 0.0005 mol/L or more,preferably from 0.005 to 2.0 mol/L.

Further, in the solution containing the oxidizing agent, a pH bufferagent or a surfactant may be incorporated in such an amount that theperformance of the pH buffer agent or the surfactant is exhibited aslong as the oxidizing action of this solution is not impaired.Incidentally, the pH of the solution containing the oxidizing agent isnot particularly limited, but is preferably from 3.0 to 10.0.

The pH buffer agent is not particularly limited, however, examplesthereof include phosphates, citrates, borates, carbonates, acetates,diethylbarbiturates, tris(hydroxymethyl)aminomethane,hydroxyethylpiperazine ethanesulfonic acid, ethylenediaminetetraaceticacid, and the like. Among these pH buffer agents, one type or two ormore types can be used.

The surfactant is not particularly limited, however, examples thereofinclude amine salt type surfactants, quaternary amine salt typesurfactants, amino acid type surfactants, betaine type surfactants,carboxylate type surfactants, sulfonate type surfactants, sulfuric acidester salt type surfactants, phosphoric acid ester salt typesurfactants, ether type surfactants, ester type surfactants,nitrogen-containing type surfactants, fluorine-containing typesurfactants, and the like. Among these surfactants, one type or two ormore types can be used. By using the surfactant, the throwing power ofplating can be improved.

A method for treating the resin with a solution containing the oxidizingagent and adsorbing the oxidizing agent on the resin surface is notparticularly limited, and for example, the resin may be immersed in thesolution containing the oxidizing agent. Conditions for immersing theresin are also not particularly limited, and for example, the resin maybe immersed in the solution at 0 to 100° C., preferably at 60 to 70° C.for 30 seconds or more, preferably for 1 to 5 minutes.

After adsorbing the oxidizing agent on the resin surface in the step(a), water washing may be performed as needed. Thereafter, the oxidizingagent adsorbed on the resin surface is activated in the step (b).

A method for activating the oxidizing agent is not particularly limited,and for example, the resin may be immersed in a solution containing onetype or two or more types of activating agents selected from the groupconsisting of an inorganic acid, an organic acid, hydrogen peroxide, ahalogen oxoacid, a halogen oxoacid salt, and a persulfate.

Among the activating agents, as the inorganic acid, for example,sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid,hydrofluoric acid, and the like are exemplified, as the organic acid,for example, acetic acid, methanesulfonic acid, and the like areexemplified, as the halogen oxoacid and the halogen oxoacid salt, forexample, potassium perchlorate, sodium periodate, perbromic acid, andthe like are exemplified, and as the persulfate, for example, sodiumperoxodisulfate, ammonium peroxodisulfate, and the like are exemplified.Among these activating agents, hydrogen peroxide, phosphoric acid, andsulfuric acid are preferred. Such an activating agent is prepared as asolution by being dissolved in a solvent such as water. The content ofthe activating agent in this solution is not particularly limited, butis, for example, 0.05 mol/L or more, preferably from 0.5 to 17 mol/L.

Further, in the solution containing the activating agent, a surfactantmay be incorporated in such an amount that the performance of thesurfactant is exhibited as long as the activating action of thissolution is not impaired. The surfactant is not particularly limited,however, examples thereof include amine salt type surfactants,quaternary amine salt type surfactants, amino acid type surfactants,betaine type surfactants, carboxylate type surfactants, sulfonate typesurfactants, sulfuric acid ester salt type surfactants, phosphoric acidester salt type surfactants, ether type surfactants, ester typesurfactants, nitrogen-containing type surfactants, andfluorine-containing type surfactants. Among these surfactants, one typeor two or more types can be used. By using the surfactant, the throwingpower of plating can be improved.

A method for activating the oxidizing agent adsorbed on the resinsurface is not particularly limited, and for example, when a solutioncontaining the activating agent is used, the resin may be immersed inthe solution at, for example, 0 to 100° C., more preferably at 60 to 70°C. for 30 seconds or more, more preferably for 1 to 5 minutes.

The above-mentioned steps (a) and (b) constitute one set, however, afterthis step (b), a neutralization and reduction treatment, a conditionertreatment, or the like may be performed as needed. Further, each of thesteps (a) and (b) is performed for preferably 30 seconds or more, morepreferably 1 to 5 minutes.

By the method of the present invention described above, a resin surfacecan be etched. Incidentally, the method of the present invention can beused for etching a resin surface in a conventionally known platingmethod on a resin, and in the other steps, a conventionally knownplating method on a resin can be used.

Examples of the conventionally known plating method on a resin includean electroless plating method and a direct plating method.

Hereinafter, a plating method on a resin using the method of the presentinvention will be described.

To a resin etched by the method of the present invention, subsequently,a catalyst is imparted using a catalyst imparting treatment solution.This catalyst imparting treatment solution is not particularly limitedas long as it is generally used for imparting a catalyst in a platingstep, but is preferably a solution containing a noble metal, morepreferably a solution containing palladium, and particularly preferablya palladium/tin mixed colloidal catalyst solution. In order to impartsuch a catalyst to the resin surface, the treatment may be performed bysetting the temperature of the catalyst imparting treatment solution to10 to 60° C., preferably 20 to 50° C. and immersing the resin thereinfor 1 to 20 minutes, preferably 2 to 5 minutes.

The resin surface to which the catalyst is imparted in this manner issubsequently subjected to metal plating such as electroless metalplating or metal electroplating (direct plating), thereby metallizingthe resin surface.

When electroless metal plating is used for metallization of the resinsurface, after the catalyst is imparted using the catalyst impartingtreatment solution, a treatment may be further performed using anactivation treatment solution containing hydrochloric acid or sulfuricacid. The concentration of hydrochloric acid or sulfuric acid in thisactivation treatment solution is 0.5 mol/L or more, preferably from 1 to4 mol/L. In order to treat the resin surface with such an activationtreatment solution, the treatment may be performed by setting thetemperature of the activation treatment solution to 0 to 60° C.,preferably 30 to 45° C. and immersing the resin therein for 1 to 20minutes, preferably 2 to 5 minutes.

The resin subjected to the catalyst impartment and activation treatmentsas described above is subsequently subjected to an electroless metalplating treatment. The electroless metal plating treatment can beperformed according to a usual method using a known electroless metalplating solution such as an electroless nickel plating solution, anelectroless copper plating solution, or an electroless cobalt platingsolution. Specifically, when the resin surface is subjected to a platingtreatment with an electroless nickel plating solution, the treatment maybe performed by immersing the resin in the electroless nickel platingsolution at pH 8 to 10 and at a liquid temperature of 30 to 50° C. for 5to 15 minutes.

Further, when metal electroplating (direct plating) is used formetallization of the resin surface, after imparting a catalyst using acatalyst imparting treatment solution, a treatment may be furtherperformed using an activation treatment solution containing copper ionsat pH 7 or higher, preferably 12 or higher. A source of the copper ionscontained in this activation treatment solution is not particularlylimited, and for example, copper sulfate is exemplified. In order totreat the resin surface with the activation treatment solution, thetreatment may be performed by setting the temperature of the activationtreatment solution to 0 to 60° C., preferably 30 to 50° C. and immersingthe resin therein for 1 to 20 minutes, preferably 2 to 50 minutes.

The resin subjected to the catalyst impartment and activation treatmentsas described above is subsequently immersed in a widely used copperelectroplating bath such as a copper sulfate bath, and may be subjectedto a treatment under usual conditions, for example, at 1 to 5 A/dm² for2 to 10 minutes.

Further, the plastic surface metallized by subjecting the resin surfaceto metal plating such as electroless plating or metal electroplating asdescribed above can also be additionally subjected to various types ofcopper electroplating or nickel electroplating or chromiumelectroplating according to need.

Incidentally, after performing the method of the present invention,water washing or hot water washing may be performed between respectivesteps.

The thus obtained resin plating has high adhesion.

EXAMPLES

Hereinafter, the present invention will be more specifically describedby showing Examples and Comparative Examples. However, the invention isby no means limited to the description thereof.

Example 1 <Formation of Electroless Nickel Plating>

As a sample, a test piece (3001M, manufactured by UMG ABS, Ltd.) of anABS resin of 50×100×3 mm was used. This sample was immersed indegreasing washing solutions PC-1 and PC-2 (manufactured by JCUCorporation) at 60° C. for 10 minutes, and subsequently immersed in asurface conditioning solution at 50° C. containing 10 ml/L ENILEX WE(manufactured by JCU Corporation) for 10 minutes.

The sample subjected to degreasing and surface conditioning was treatedin an etching step shown in Table 1, and further immersed in aconditioner (catalyst impartment enhancing) treatment solution D-POP CDV(manufactured by JCU Corporation) at 25° C. for 1 minute.

Incidentally, the etching solution used in the etching step shown inTable 1 is as follows.

Chromic Acid Etching (Conventional Method)

-   -   anhydrous chromic acid: 3.8 mol/L    -   sulfuric acid: 3.8 mol/L    -   liquid temperature: 68° C.

Method of the Present Invention

Step (a)

-   -   potassium permanganate: 0.3 mol/L    -   fluorine-containing type surfactant MISTSHUT PF (manufactured by        JCU Corporation): 2 ml/L    -   boric acid/sodium tetraborate buffer solution: 10 ml/L    -   liquid temperature: 68° C., pH: 6.5

Step (b)

-   -   sulfuric acid: 10 mol/L    -   fluorine-containing type surfactant MISTSHUT PF (manufactured by        JCU Corporation): 2 ml/L    -   liquid temperature: 68° C., pH: 1.0 or lower

Subsequently, the sample was immersed in a palladium/tin mixed colloidalcatalyst solution at 35° C. containing 20 ml/L CT-580 (manufactured byJCU Corporation) and 2.5 mol/L hydrochloric acid for 4 minutes, therebyimparting the catalyst on the ABS resin. The sample to which thecatalyst was imparted was immersed in an activation treatment solutionat 35° C. composed of 1.2 mol/L hydrochloric acid for 4 minutes, therebyactivating the catalyst, and subsequently immersed in an electrolessnickel plating solution ENILEX NI-100 (manufactured by JCU Corporation)at pH 8.8 and 35° C. for 10 minutes, thereby performing electrolessnickel plating until the film thickness reached 0.5 μm on the ABS resin.

<Peel Strength Measurement and Sample Preparation Method> (JIS H 8630Appendix 6)

After the sample subjected to electroless nickel plating wassufficiently washed by water washing or hot water washing, the samplewas immersed in an acid active solution V-345 (manufactured by JCUCorporation) at room temperature for 1 minute. Subsequently, accordingto JIS H 8630 Appendix 6, copper sulfate plating EP-30 (manufactured byJCU Corporation) was performed until the film thickness reached 20 μm.Thereafter, the resulting material was annealed at 70° C. for 1 hour,and an adhesion strength was measured using a tensile strength testerAGS-H 500N (manufactured by Shimadzu Corporation).

<Heat Shock Test and Sample Preparation Method>

After the sample subjected to electroless nickel plating wassufficiently washed by water washing or hot water washing, the samplewas immersed in an acid active solution V-345 (manufactured by JCUCorporation) at room temperature for 1 minute. Subsequently, coppersulfate plating CU-BRITE EP-30 (manufactured by JCU Corporation) wasperformed until the film thickness reached 20 μm by an electroplatingmethod. Further, semi-glossy nickel plating CF-24T (manufactured by JCUCorporation) was performed until the film thickness reached 10 μm, andfurther, glossy nickel plating #88 (manufactured by JCU Corporation) wasperformed until the film thickness reached 10 μm, and further,microporous nickel plating MP-309 (manufactured by JCU Corporation) wasperformed until the film thickness reached 1 μm. Finally, glossychromium plating EBACHROM E-300 (manufactured by JCU Corporation) wasperformed until the film thickness reached 0.2 μm, whereby respectiveplating films were sequentially formed. Thereafter, the resultingmaterial was annealed at 70° C. for 1 hour.

The above sample was subjected to a 40-cycle (cyc) or 80-cycle heatshock test in which a step of maintaining the sample at −30° C. for 30minutes and maintaining the sample at 70° C. for 30 minutes was regardedas one cycle. The sample in which swelling did not occur in the platingfilm was evaluated as “A”, and the sample in which swelling occurred wasevaluated as “B”.

<Results>

TABLE 1 Number of Treatment time Peel strength Heat shock test etchingsteps Step (a) Step (b) (kgf/cm) 40 cyc 80 cyc Comparative Method 1chromic acid etching for 2 min 1.1 B B Comparative Method 2 chromic acidetching for 10 min 1.2 A A Comparative Method 3 1 2 2 1.1 B BComparative Method 4 1 10 20 1.0 B B Comparative Method 5 1 20 20 0.9 BB Example Method 1 2 2 2 1.2 A B Example Method 2 5 2 2 1.1 A A ExampleMethod 3 10 2 2 1.2 A A

It was found that the adhesion is improved by extending the treatmenttime in the case of chromic acid etching of the conventional method,however, the adhesion is not improved even if the treatment time issimply extended in the etching step of the method of the presentinvention. It was found that the adhesion is improved by repeatedlyperforming the etching step even in a short treatment time.Incidentally, even in the case of Example Method 1, by repeating the setof the steps (a) and (b) five times, “A” was obtained in the severer80-cycle heat shock test.

Example 2

Electroless nickel plating was performed in the same manner as inExample 1 except that, in Example Method 1 of Example 1, the pH of theetching solution used in the step (a) was changed as shown in Table 2,and as the pH buffer solution, a buffer solution shown in Table 3 wasused according to the pH. Incidentally, in the adjustment of the pH,sodium hydroxide and sulfuric acid were used. Further, for theelectroless nickel plating, peel strength measurement and a heat shocktest were performed in the same manner as in Example 1. The results areshown in Table 2.

TABLE 2 Peel strength Heat shock test pH (kgf/cm) (40 cyc) ExampleMethod 4* 13.0 1.1 A Example Method 5 12.0 1.2 A Example Method 6 9.01.1 A Example Method 7 6.5 1.2 A Example Method 8 5.0 1.3 A ExampleMethod 9 3.0 1.1 A Example Method 10 1.0 1.2 A *The set of the steps (a)and (b) was performed five times.

TABLE 3 pH pH buffer solution 10.0 or higher carbonate/bicarbonatebuffer solution 5.5 to 10.0 boric acid/sodium tetraborate buffersolution 2.5 to 5.5 acetic acid/sodium acetate buffer solution 2.5 orlower phosphoric acid/sodium dihydrogen phosphate buffer solution

In the method of the present invention, there was no problem at any pH.

Example 3

Electroless nickel plating was performed in the same manner as inExample 1 except that, in Example Method 1 of Example 1, the pH bufferagent was removed from the solution used in the steps (a) and (b). Whenthis electroless nickel plating was subjected to peel strengthmeasurement and a heat shock test in the same manner as in Example 1,the same results as in Example Method 1 were obtained.

Example 4

Electroless nickel plating was performed in the same manner as inExample 1 except that, in Example Method 1 of Example 1, a test piece(3001M, manufactured by UMG ABS, Ltd.) of an ABS resin of 50×180×3 mm ina three-dimensional shape (a shape that makes air easy to remain) wasused as the sample, and a surfactant shown in Table 4 was used in thesolution used in the steps (a) and (b). The appearance of theelectroless nickel plating was evaluated by visual observation. Theresults are shown in Table 4.

TABLE 4 Appear- Surfactant ance Example Method 11* non good ExampleMethod 12 fluorine-containing type surfactant good MISTSHUT PF(manufactured by JCU Corporation): 2 ml/L Example Method 13 cationicsurfactant PB-117 (manufac- good tured by JCU Corporation): 2 ml/LExample Method 14 anionic surfactant #82 (manufactured good by JCUCorporation): 2 ml/L Example Method 15 nonionic surfactant CHT-111A good(manufactured by JCU Corporation): 2 ml/L Example Method 16 amphotericsurfactant Gulanlubu SE good (manufactured by JCU Corporation): 2 ml/L*The set of the steps (a) and (b) was performed five times.

In the method of the present invention, plating was performed on theresin in a three-dimensional shape with a small number of times by usinga surfactant.

INDUSTRIAL APPLICABILITY

According to the method of the present invention, a resin surface can beetched, and therefore, the method can be used in a conventionally knownplating method on a resin.

1: A resin surface etching method, wherein, in etching a resin surface,one of steps (a) and (b) is performed two or more times withoutperforming a resin swelling step: (a) a step of treating the resinsurface with a solution comprising an oxidizing agent and adsorbing theoxidizing agent on the resin surface; and (b) a step of activating theoxidizing agent adsorbed on the resin surface in the step (a). 2: Theresin surface etching method according to claim 1, wherein each of thesteps (a) and (b) is performed for 30 seconds or more. 3: The resinsurface etching method according to claim 1, wherein the oxidizing agentused in the step (a) is permanganic acid or a salt thereof. 4: The resinsurface etching method according to claim 1, wherein the activation ofthe oxidizing agent in the step (b) is performed by a treatment with asolution comprising one or more types of activating agents selected fromthe group consisting of an inorganic acid, an organic acid, hydrogenperoxide, a halogen oxoacid, a halogen oxoacid salt, and a persulfate.5: The resin surface etching method according to claim 1, wherein theactivation of the oxidizing agent in the step (b) is performed by atreatment with a solution comprising one or more types of activatingagents selected from the group consisting of sulfuric acid, phosphoricacid, hydrochloric acid, nitric acid, methanesulfonic acid, hydrogenperoxide, peroxodisulfate, periodic acid, perchloric acid, and perbromicacid. 6: A plating method on a resin, wherein, in plating a resin, theplating is performed after the resin is etched by the resin surfaceetching method according to claim 1 without performing a resin swellingstep.